*{
    margin: 0;
    padding: 0;
}
img{
    outline-width:0px;  
    vertical-align:top;  
}
html,body{
    width: 100%;
    height: 100%;
}
.bg_img img{
    width: 100%;
}
.bg_img{
    position: relative;
}
.bg_img .nav{
    position: absolute;
    right: 10vw;
    top: 3vw;
}
.bg_img .nav li{
    float: left;
    margin-left: 5.5vw;
    font-size:1.5vw;
    font-family:Source Han Sans CN;
    font-weight:500;
    color:rgba(255,255,255,1);
    cursor:pointer;
}
.contact ul{
    background:rgba(241,241,245,1);
    padding: 0rem 10vw 10vw;
    display: flex;
    justify-content: space-between;
    position: relative;
}
.contact li{
   float: left;
   width: 24%;
}
.contact li img{
    width: 100%;
}
.contact ul .backTop{
 position: absolute;
 bottom: 2vw;
 right: 4vw;
 width: 6vw;
 cursor:pointer;
}